Benign Prostatic Hyperplasia (BPH), also known as benign prostatic hypertrophy, refers a disease in which prostate epithelial cells grow abnormally which result in a non-cancerous enlargement of the prostate gland. BPH typically occurs in middle-age and elderly men, and is very common. It afflicts more than 10 million adult males in the United States, and many millions more throughout the rest of the world. Half of all men over 50 develop symptoms of BPH. The enlargement of the prostate gland may result in compression of the urethra, resulting in difficult, urgent, and frequent urination. If left untreated, it may result in urinary tract infections, urinary bladder stones, or renal failure.
Until relatively recently, surgical intervention to remove the prostate was the only treatment of the disease, and even today, surgery is the treatment of last resort, almost inevitably relied upon when other treatments are not, or cease to be, effective. Prostate surgery and recovery therefrom is painful, and the surgery itself may not be effective and poses the risk of serious side effects, including bleeding, infection, and impotence. For a recent review, see Barry et al., 2001, “Measuring the symptoms and health impact of benign prostatic hyperplasia and its treatments” Benign Prostatic Hyperplasia (5th International Consultation on BPH). Health Publication, Ltd.
Only two classes of drugs are currently available to treat the symptoms of BPH: Alpha blockers and 5-alpha reductase inhibitors. 5-alpha reductase inhibitors, such as Finasteride (Proscar) work to slow prostate growth by blocking production of compounds that inhibit production of the active form of testosterone (dihyrdotestosterone or DHT). Use of drugs in this class can cause a loss of libido, sexual dysfunction. and loss of muscle mass and tone in males and is associated with an increased occurrence of high grade prostate cancer. In addition, this therapy is limited by the very long delay (months) between first administering the drug and significant reduction in prostate size in the patient.
Alpha blockers, such as Terazosin (Hytrin), act by relaxing the smooth muscles, allowing urine to pass through the urethra more freely. While this class of drugs reduces symptoms more rapidly than the first, it does not treat the disease by reducing the size of the prostate or preventing it from growing larger, which can lead to eventual surgical intervention. Side effects include dizziness, light-headedness and fatigue.
Thus, there is a significant, unmet need for drugs that can treat the underlying disease condition of BPH without serious side effects. The present invention meets that need.
Prostate carcinoma is the most common cancer diagnosed in men in the United States and has the second highest cancer death rate yielding only to lung adenocarcinoma. Parker et al., CA Cancer J. Clin. 46:5-27 (1996). Although it is possible to effectively treat organ-confined prostate cancer, there are very limited treatment options for metastatic disease. Thus, it is of great importance to find novel ways to diagnose early stage disease and to closely monitor both progression and treatment of the disease, as well as to develop new therapeutic approaches. To achieve this, it is important to understand the molecular mechanisms of prostate cancer development and to identify new biochemical markers for disease diagnosis and progression.
To date there are very few prostate-specific markers available. The best-known and well-characterized markers of proven prostate cancer diagnostic value are the proteins prostatic acid phosphatase (PAP), prostate specific antigen (PSA), and prostate-specific membrane antigen (PSMA). Each of these proteins has also become the target for novel immunotherapy approaches to the treatment of disease. Horoszewicz et al., Anticancer Res. 7:927-935 (1987); Barren et al., Prostate 30:65-68 (1997); Murphy et al., Prostate 33:281-285 (1997); Murphy et al., Prostate 26:164-168 (1995); Rochon et al., Prostate 25:219-223 (1995); Correale et al., J. Immunol. 161:3186-3194 (1998); and Murphy et al., Prostate 38:73-78 (1999).
It has been reported that a cation channel protein, variously designated Trp-p8 (transient receptor potential-p8), TRPM8, and CMR1 (cold and menthol receptor 1), is preferentially expressed in prostate. Cloning of the full-length human Trp-p8 cDNA revealed a transcript corresponding to an 1104 amino acid polypeptide sharing homology with the trp family of calcium channels. Clapham et al., Nature Reviews 2:387-396 (2001) and Clapham et al., IUPHAR Compendium, TRP Channels (2002). Trp-p8 shows particularly high homology with the human TRPC7 gene—a putative Ca2+ channel protein of the trp family that is highly expressed in brain tissue. Nagamine et al., Genomics 54:124-131 (1998). Trp-p8 also shows significant homology to human melastatin, another Trp family-related protein expressed in melanocytes and believed to be a tumor suppressor gene. Duncan et al., Cancer Res. 58:1515-1520 (1998) and Hunter et al., Genomics 54:116-123 (1998). Perhaps of greatest interest is the observation that the Trp-p8 gene appears to be expressed in a large spectrum of nonprostatic, in addition to prostatic, neoplastic lesions. Tsavaler et al., Cancer Res. 61(9):3760-9 (2001).
The Trp superfamily comprises more than 20 related cation channel proteins that have been implicated in processes including sensory physiology to vasorelaxation and male fertility. Defects in Trp channels have been associated with changes in growth control and tumor suppression. While all Trp proteins are calcium channels, they vary significantly in their selectivity and mode of activation. Members of the Trp superfamily share significant sequence homology and predicted structural similarities, such as size of predicted transmembrane segments.
Trp-p8 is over-expressed in a range of cancers including prostate, breast, lung and colon, while within normal tissues, it is predominantly expressed in human prostate [Tsavaler et al., supra] and dorsal root ganglia (DRG), (Dendreon, unpublished observation). Fuessel et al. reported that Trp-p8 is a highly prostate-specific and prostate carcinoma-associated gene thus qualifying it as a potential target for specific therapies. International J. of Oncology 23:221-228 (2003). Among other species, Trp-p8 orthologues are reportedly expressed in a subset of DRG and trigerminal ganglia (TG) neurons in rat [McKemy et al., Nature 416(6876):52-8 (2002)] and mouse [Peier et al., Cell 108(5):705-15 (2002)] as well. Thus, Trp-p8 is a pantumor-expressed marker with significant potential use in disease diagnosis and monitoring of disease progression during treatment as well as a viable target for cancer therapy.
Association of Trp-p8 with prostate, lung, breast, and colon cancers and the important role various ion channels play in vital cell functions suggest that the Trp-p8 channel may have a significant function in cancer cell signaling and/or proliferation. Modulation of Trp-p8 activity, either by activating via an agonist or inhibiting via an antagonist, at a physiological temperature can be valuable as a therapeutic to manipulate the Trp-p8 expressing cells in a specific manner. See for example U.S. patent application Ser. No. 10/923,413.
Accordingly, there remains a need in the art for small-molecule modulators of Trp-p8 activity, compositions comprising one or more small-molecule Trp-p8 modulators, and methods for the identification and use of small-molecules for modulating the activity of Trp-p8 in a cell and for the treatment of disease associated with the aberrant expression of Trp-p8.